1. Field of the Invention
The present invention relates to an ink composition suitably used for inkjet recording, and an inkjet recording method, a printed material, and a process for producing a molded printed material employing the ink composition.
2. Description of the Related Art
As image recording methods for forming an image on a recording medium such as paper based on an image data signal, there are an electrophotographic system, sublimation type and melt type thermal transfer systems, an inkjet system, etc. In the electrophotographic system, a process of forming an electrostatic latent image on a photosensitive drum by electrically charging and exposing is required, and the system is complicated; as a result, there is the problem that the production cost is high. With regard to the thermal transfer system, although the equipment is inexpensive, due to the use of an ink ribbon there is the problem that the running cost is high and waste material is generated.
On the other hand, with regard to the inkjet system, the printing equipment is inexpensive, it is not necessary to use a plate when printing, and since an image is formed directly on a recording medium by discharging an ink only on a required image area, the ink can be used efficiently and the running cost is low particularly in the case of small lot production. Furthermore, there is little noise and it is excellent as an image recording system, and has been attracting attention in recent years.
Among them, an inkjet recording ink (radiation-curing inkjet recording ink), which is curable upon exposure to radiation such as UV rays, is an excellent system from the viewpoint of it being printed on various types of substrates because of the drying properties being excellent, compared with a solvent-based ink since the majority of the ink components cure upon exposure to radiation such as UV rays, and an image is resistant to spreading.
There is a demand for an ink composition contained in a radiation-curing ink to cure at high sensitivity in order to form an image with high image quality.
By achieving high sensitivity for the ink composition, high curability upon exposure to actinic radiation can be imparted, and there are therefore provided various benefits such as a reduction in power consumption, a longer lifetime of an actinic radiation generator due to a decrease in the load thereon, and suppression of evaporation of uncured low-molecular-weight material and of a reduction in the strength of an image formed. There is also a desire for an ink composition that gives an image (printed material) that is resistant to cracking, peeling-off, etc., and gives a cured coating that has excellent impact resistance, flexibility, and adhesion to a substrate. A cured coating having high flexibility, impact resistance, and adhesion to a substrate enables a printed material to be displayed and stored for a long period of time in various environments while maintaining high image quality, and also has advantages such as ease of handling of the printed material.
As an ink composition, a polymerizable monomer-containing actinic radiation-curing ink for inkjet which comprises as polymerizable monomers, relative to the total polymerizable monomers, 95 to 99.99 wt % of a monofunctional monomer and 0.01 to 5 wt % of a polyfunctional monomer, and for which the ductility of a cured coating exceeds 120%, has been disclosed (International Patent Application WO 2007/013368).
Furthermore, as an ink composition, an ink composition comprising an N-vinyllactam has been disclosed (Japanese Registered Patent No. 2880845). Moreover, as an ink composition that is curable upon exposure to radiation such as UV rays, an ink composition having excellent adhesion has been disclosed (ref. JP-PCT-2004-514014 (JP-PCT denotes a published Japanese translation of a PCT application)).